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Check Engine Light P0420/P0430 on 2017 Challenger GT - Catalytic Converter?

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Mike T. · rep 0 · May 25, 4:15 AM · 1 replies · solved · Question

Vehicle: 2017 Dodge Challenger GT

My 2017 Dodge Challenger GT, with about 70,000 miles, just threw a Check Engine Light, and when I scanned it, I got both P0420 and P0430 codes. From what I understand, these usually point to catalytic converter efficiency issues on both banks. I haven't noticed any dramatic loss of power, but sometimes it feels a little sluggish, and I've caught a slight exhaust smell, especially after driving for a while.

I'm worried this is going to be an expensive repair. Is there anything else that could cause these codes besides a bad catalytic converter? I've heard oxygen sensors can sometimes trick the system. What's the best way to diagnose this without just throwing parts at it? Any advice for a Challenger owner dealing with this would be appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 4:15 AM

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The P0420 (Catalyst System Efficiency Below Threshold - Bank 1) and P0430 (Catalyst System Efficiency Below Threshold - Bank 2) codes indeed strongly suggest an issue with your catalytic converters. These codes are triggered when the post-catalytic converter oxygen sensor detects that the converter isn't efficiently storing oxygen, meaning it's not effectively cleaning the exhaust gases.

While catalytic converters are the primary suspects, it's important to rule out other potential causes before jumping to replacement:

  1. Oxygen Sensors (O2 Sensors): Faulty O2 sensors, particularly the downstream (post-cat) sensors, can sometimes inaccurately report catalyst efficiency. However, if both P0420 and P0430 are present, it's less likely to be two coincidentally failed O2 sensors and more likely a systemic issue.
    • Diagnostics: A technician can monitor the live data from both upstream and downstream O2 sensors using a scan tool. The downstream sensor's voltage should be relatively stable compared to the fluctuating upstream sensor if the converter is working correctly.
  2. Exhaust Leaks: An exhaust leak before or near the downstream O2 sensor can introduce ambient air, skewing sensor readings and potentially triggering these codes. The slight exhaust smell you've noticed could be a clue.
  3. Engine Misfires or Rich/Lean Conditions: Persistent engine problems like misfires (P030x codes), excessive oil consumption, or running too rich/lean (P0171/P0174 codes) can damage catalytic converters over time by introducing unburnt fuel or contaminants. Ensure your engine is running optimally.

When to See a Shop: You should take your 2017 Challenger GT to a trusted mechanic or dealership for a thorough diagnosis. They will perform:

  • Visual Inspection: For exhaust leaks, damaged converters, or wiring issues.
  • Scan Tool Analysis: Live data monitoring of O2 sensors and fuel trims.
  • Exhaust Backpressure Test: To check if the converters are clogged, which can also cause sluggishness. It's crucial to diagnose the root cause, as simply replacing the converters without addressing an underlying issue (like an engine problem or exhaust leak) will likely lead to the new converters failing prematurely.
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